Transmission ratio = the rotational speed of the driving wheel divided by the rotational speed of the driven wheel = the ratio of the reciprocal of their graduation circle diameters. That is, i=n 1/n2=D2/D 1.
I=n 1/n2=z2/z 1 (gear)
For multi-stage gear transmission; The transmission ratio between every two shafts is calculated according to the above formula. The total transmission ratio from the first shaft to the nth shaft is equal to the product of the transmission ratios of all stages.
When the angular velocity in the formula is averaged, the obtained transmission ratio is the average transmission ratio. Theoretically, for most gear drives with correct involute profile, the instantaneous transmission ratio is constant; For chain drive and friction wheel drive, the instantaneous transmission ratio changes.
Extended data:
The distribution of transmission ratio of multi-stage reducer directly affects the bearing capacity and service life of reducer, and also affects its volume, weight and lubrication. The transmission ratio is generally allocated according to the following principles: to make the bearing capacity of all levels of transmission roughly equal; Make the reducer smaller in size and mass; Make the peripheral speed of gears at all levels smaller; When oil bath lubrication is used, the oil immersion depth of the big gears of each gear pair is relatively small.
Compared with strength, the oil immersion depth of all gears is almost the principle of secondary distribution. Even if the high-speed gear is not soaked in oil, it can be fully lubricated through structural design.
In multi-stage gear reduction transmission, the distribution of transmission ratio will directly affect many technical and economic indexes of transmission. For example, the profile size and quality of the transmission largely depend on the size of the low-speed gear, and the lower transmission ratio of the low-speed gear is beneficial to reduce the profile size and quality.
In closed transmission, gears are mostly lubricated by splashing oil. In order to avoid the excessive increase of oil loss caused by the excessive oil immersion depth of large-diameter gears when the diameters of large gears at all levels are very different, it is often hoped that the diameters of large gears at all levels are similar. Therefore, properly increasing the transmission ratio of high-speed gears is conducive to reducing the diameter difference of all gears.
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